Air classifier



Dec. 8, 1931. A, H, s s 1,834,982

AIR CLASSIFIER Filed April 8, 1930 2 Sheets-Sheet l l//V TO R wywwdATTORNEY Dec. 8, 1931.

A. H. STEBBINS 1,834,982

AIR CLASSIFIER Filed April 8, 1930 2 Sheets-Sheet 2 Fig. 3

21 M/XI 1P 3? j jfflx 16k 1 M H a T 25 l/vl/fA/TOR'" Mix 57 if MMATTORNEY Patented Dec. 8, 1931 PATENT OFFICE ALBERT H. STEBBINS, LOSANGELES, CALIFORNIA AIR GLASSIFIER Application filed April 8, 1930.Serial No. 442,570.

The invention relates to air classifiers of the cei'ltrifugal type andmore particularly to means for promoting a rotative movement of the airwithin the classifying receptacle.

In air classifiers of this general type it is desirable that the air andmaterials to be separated be introduced into the receptacle to rotatetherein at high speed, and the present invention relates to:improvements in the means for introducing the materials and air into thereceptacle so that this air stream will impart the desired rotativemovement to the volume of air within the receptacle.

An important feature of the present inven tion therefore resides inmeans for delivering an air stream into the receptacle in a spiraldownwardly extending direction so that it encircles the volume of airwithin the receptacle throughout a relatively large area and graduallymerges with the air within the re ceptacle to impart its rotativemovement to this volume of air.

This desired result is secured in the embodiment of the inventionillustrated by provid- {5 ing the air classifying receptacle with an airinlet pipe that extends spirally about the receptacle in a downwarddirection and is arranged so that its spiral coils extend graduallyinwardly through the side of the recep- 0 tacle and pass from theexterior to the interior of the receptacle, to thereby direct the airstream spirally around the receptacle and guide it along a spiraldownwardly extending path within the receptacle.

The above and other features of the invention and novel combination ofparts will be hereinafter described in connection with the accompanyingdrawings illustrating one good practical form thereof.

In the drawings Fig. 1 is a side elevation of an air classifierconstructed in accordance with the present invention;

Fig. 2 is a perspective view with parts in section of the lower portionof the air classitier of Fig. 1;

Fig. 3 is a sectional view taken on the line 3-3 of Fig. 1;

Fig. 4 is an enlar ed sectional view taken on the line 4-4 of I ig. l,and

Fig. 5 is a vertical sectional view taken on the line 5-5 of Fig. 2.

The classifying receptacle into which air and the materials to beseparated are delivered may be variously constructed so that thematerial laden air may rotate therein to throw the heavier materialsoutwardly by centrifugal force against the side Walls of the receptacleto move downwardly adjacent these walls under the influence of gravity,but in many cases it is desirable to so construct the classifyingreceptacle that it converges in a downward direction so that the heaviermaterials are directed inwardly towards the central axis of thereceptacle as they move downwardly therein.

In the embodiment of the invention illustrated in the drawings theclassifying receptacle has the general downwardly convergmg constructionjust mentioned so that the lower portion 10 of the classifyingreceptacle is relatively small while the upper portion 11 thereof ismuch larger in diameter and constitutes an expansion chamber in whichthe air may expand to promote the settling of the heavier particles outof the air stream. The upper annular portion 11 of the receptacle hasextending downwardly therefrom the downwardly converging portion 12 andthe lower end of this down wardly converging portion 12 is connected tothe intermediate or drum-like portion 13, and below this drum-likeportion 13 the receptacle is provided with several inwardly steppedportions 14- of reduced diameter as shown.

The upper end of the classifying recep tacle is closed and has theexhaust pipe 15 leading from the central portion thereof. This exhaustpipe may lead direct to the suction side of'an exhaust fan or may leadto an exhaust pipe 16 as shown.

The materials to be treated may be supplied to the classifier of thepresent invention by a feed pipe 17 through which air bearing thematerials to be treated is ad-. vanced along the pipe either by suctionor blast means. This material bearing air may be supplied to the pipe 17from a preceding machine or other source of supply, but in theembodiment of the invention shown the materials to be treated aresupplied to the air inlet pipe 17 by a feed hopper 18 having theadjustable gate 19 adapted to regulate the flow of the materials fromthe feed hopper into the pipe 17. Air from the atmosphere is preferablyintroduced into the pipe 17 near the feed hopper 18 so that it Wlll helpromote the fiow of the materials from the hopper into the feed pipe, andin the construction shown the pipe 17 is provided at its outer end withthe air inlet apertures 20 through which air is drawn into the pipe bythe suction produced Within the receptacle by the exhaust pipe 15,

The feed pipe 17 in accordance with the present invention extendsspirally about the air classifier in a downward direction andcommunicates with the receptacle throughout a substantial portion of itslength, the arrangement being such that the material laden air streamWithin the pipe 17 is directed spirally about the classifying receptacleand may gradually move inwardly into the receptacle to merge with theair therein and impart rotative movement to the volume of air.

The feed pipe 17 as shown is formed with a plurality of spiralssurrounding the classifying receptacle and these. sp rals gradually passinwardly from the exterior to the interior of the classi ier so as toguide the air stream in a downward spiral direction after it enters thereceptacle.

In the construction shown the stream of air supplied by the feed pipe 17is confined in this pipe throughout a portion ofthe uppermost coil andthe wall between this spiral coil and the classifying receptacle is cutaway at a point indicated by 21 as part way around this upper coil; thatis, the air stream is permitted to pass inwardly and intermingle withthe volume of air in the classifier from the point 21 downwardlythroughout the remaining portion of the spirally d1sposed feed pipe. Asabove stated the spiral coils of the feed pipe gradually pass inwardlythrough the wall of the receptacle and the outer curved wall of thespiral pipe merges with the outer wall of the portion 13 of the airclassifier at the point indicated by 22. From the oint 22 onward theupper spiral wall 23 of the spiral feed pipe is disposed at the innersurface of the classifying receptacle and constitutes a spiral guide fordirecting the air stream downwardly along its spiral path within the airclassifier.

The lower wall 24 of the spiral feed pipe, in the construction shown issecured to the classifying receptacle between the stepped portions 13and 14 thereof, the arrangement being such that the spaced spirallydisposed walls 23 and 24: within the lower portion of the receptacleform a well defined spiral path therein for guiding the air streamdownwardly within the receptacle into the lower portion thereof as willbe apparent from the drawings.

The material laden air drawn inwardly along the feed pipe 17 as a resultof the suction produced in the air classifier by the pipe 15, or byblast means (not shown) will be directed downwardly in a spiral pathwithin the classifying receptacle and since this feed pipe is providedwith a plurality of spiral coils passing repeatedly around the interiorof the receptacle they produce a well defined spiral passage which willserve to direct the air stream downwardly in a spiral path about thevolume of air to impart the desired r0 tative movement to the air withinthe receptacle. The heavier particles within the air stream will bethrown outwardly against the outer curved wall of the spiral pipe and asthey travel downwardly along the different coils of this pipe they willpass from the lower end thereof into the reduced lower portion 10 andthen into the collecting hopper "25 from which they may be dischargedfrom time to time in a Well known manner.

The portion of the spirally traveling air stream which gradually worksinwardly and intermingles with the volume of air within the receptaclewill have the heavier paiticles removed therefrom by the centrifugalaction just mentioned, but the larger particles which pass from the airstream into the volume of air in the receptacle will be subjected to afurther centrifugal action by the rotative movement of the entire volumeof air to further promote the separation of the coarser from the finerparticles within the classifying receptacle.

. It may be desirable to introduce a small amount of air into the lowerportion of the receptacle to pass upwardly therein to thereby producerising air currents which will. help to pick up the lighter particlesthat may tend to work downwardly into the discharge hopper 25. This isaccomplished by providing the lower portion of the receptacle with theair inlet slots or apertures 26, through which air may enter from theatmosphere, and these apertures are preferably so constructed that theywill direct the air substantially tangentially into the receptacle tothereby promote the whirling movement of the air within the receptacle.

It will be seen from the foregoing that as a result of the presentconstruction whereby the air stream is guided spirally about the Volumeof air within the receptacle this air stream is given ampleopportin'iity to impart its rotative movement to the volume of air tocause all the air within the receptacle to rotate rapidly and therebyefiect the desired centrifugal separation of the materials beingtreated.

The materials carried along the feed pipe 17 by the stream of air maytend to settle particles that tend to settle along the lower wall 24 ofthe pipe.

' ing an air inlet What is claimed is:

1. An air classifier, comprising in combination, a downwardly extendingreceptacle, means for delivering an air stream carrying the materials tobe separated into the receptacle with a rotative movement that imparts arotative whirling movement to the volume of air within the receptacle,including an air inlet pipe extending spirally downwardly about thereceptacle and througha side wall thereof to project inwardly from theinner wall of the receptacle, and adapted to guide the stream ofmaterial laden air into the receptacle and in a downwardly spiral paththerein, and means for removing air from the upper end of thereceptacle.

2. An air classifier, comprising in combination, a downwardly convergingreceptacle, means for delivering an air stream carrying the materials tobe separated into the receptacle with a rotative movement that imparts arotative whirling movement to the volume of air within the receptacle,including an air inlet pipe extending spirally downwardly about the recetacle to guide the stream of material la en air into the receptacle andprovided with a downwardly extending spiral portion that projectsinwardly ,from the inner wall of the receptacle to guide the air streamupon entering the receptable along a downwardly extending spiral path,and means for removing air from the upper end of the receptacle.

3. An air classifier, comprising in combination, a downwardly convergingreceptacle, means for delivering an air stream carrying the materials tobe separated into the receptacle with a rotative movement that imparts arotative whirling movement to the volume of air within the receptacle,includpipe extending s irally downwardly about the rece tacle an openinginto the rece tacle throug out a substantial portion of its s irallength, and means for removm a1r rom the upper portion of the re ceptace.

4. An air classifier,

comprising in combination, a downwardly extending receptacle, means fordelivering an air stream carrying the materials to be separated into thereceptacle with a rotative movement that imparts a rotative whirlingmovement to the volume of air within the receptacle including an airinlet pipe extendin spiraliy downwardly in a plurality of coils aboutthe receptacle and opening into the receptacle along its spiral length,and means for removing air from the upper portion of the receptacle.

5. An air classifier, comprising in combination, a downwardly extendingreceptacle, means for delivering an air stream carrying the materials tobe separated into the receptacle with a rotative movement that im--parts a rotative whirling movement to the volume of air within thereceptacle, including an air inlet pipe extending spirally downwardlyabout the receptacle in communication therewith and provided with acooperating spiral wall extendin inwardly from the inner wall of thereceptac e to guide the air stream downwardly in a spiral path, andmeans for removing air from the upper portion of the receptacle.

6. An air classifier, comprising in combination, a downwardly extendingreceptacle, means for delivering an air stream carrying the materials tobe separated into the receptacle with a rotative movement that imparts arotative whirling movement to the volume of air within thereceptacle,including an air inlet pipe extending spirally downwardly about thereceptacle to direct the air stream along a spiral downwardly extendingpath within the receptacle and provided with air inlet apertures in itslower wall, and

means for removing air from the upper portion of the receptacle.

7. An air classifier, comprising in combination, a downwardly extendingreceptacle, means for delivering an air stream carrying the materials tobe separated into the re-' ceptacle with a rotative movement that im-/parts a rotative whirling movement to the volume of air within thereceptacle, including an air inlet pipe extending spirally about thereceptacle in a' downwardly direction and provided with a gradually fromthe outside to the inside of the receptacle, and means for removing air"from the upper portion of the receptacle.

8. An air classifier, comprising in combination, a receptacle havinspirally arranged portions that are stepped inwardly to reduce thediameter of the lower portion of the receptacle, means for delivering anair stream carrying the materials to be separated into the receptaclewith a rotative movement to impart a rotative whirling movement to thevolume of air in the receptacle, including an plurality of coils thatpass air inlet pipe extending spirally downwardly about the receptacleand into the interior of the receptacle to cooperate with said spiralstepped portion and adapted to guide the stream of material laden airinto the receptacle and downwardly therein along a spiral path, andmeans for removin air from t e upper portion of the receptac e.

In testimony whereof, I have signed my name to this specification.

ALBERT H. STEBBINS.

